<?php
// CRC16-CCITT validator
class CRC
{

    private $crc_table = array(
        0x0,
        0x1021,
        0x2042,
        0x3063,
        0x4084,
        0x50a5,
        0x60c6,
        0x70e7,
        0x8108,
        0x9129,
        0xa14a,
        0xb16b,
        0xc18c,
        0xd1ad,
        0xe1ce,
        0xf1ef,
        0x1231,
        0x210,
        0x3273,
        0x2252,
        0x52b5,
        0x4294,
        0x72f7,
        0x62d6,
        0x9339,
        0x8318,
        0xb37b,
        0xa35a,
        0xd3bd,
        0xc39c,
        0xf3ff,
        0xe3de,
        0x2462,
        0x3443,
        0x420,
        0x1401,
        0x64e6,
        0x74c7,
        0x44a4,
        0x5485,
        0xa56a,
        0xb54b,
        0x8528,
        0x9509,
        0xe5ee,
        0xf5cf,
        0xc5ac,
        0xd58d,
        0x3653,
        0x2672,
        0x1611,
        0x630,
        0x76d7,
        0x66f6,
        0x5695,
        0x46b4,
        0xb75b,
        0xa77a,
        0x9719,
        0x8738,
        0xf7df,
        0xe7fe,
        0xd79d,
        0xc7bc,
        0x48c4,
        0x58e5,
        0x6886,
        0x78a7,
        0x840,
        0x1861,
        0x2802,
        0x3823,
        0xc9cc,
        0xd9ed,
        0xe98e,
        0xf9af,
        0x8948,
        0x9969,
        0xa90a,
        0xb92b,
        0x5af5,
        0x4ad4,
        0x7ab7,
        0x6a96,
        0x1a71,
        0xa50,
        0x3a33,
        0x2a12,
        0xdbfd,
        0xcbdc,
        0xfbbf,
        0xeb9e,
        0x9b79,
        0x8b58,
        0xbb3b,
        0xab1a,
        0x6ca6,
        0x7c87,
        0x4ce4,
        0x5cc5,
        0x2c22,
        0x3c03,
        0xc60,
        0x1c41,
        0xedae,
        0xfd8f,
        0xcdec,
        0xddcd,
        0xad2a,
        0xbd0b,
        0x8d68,
        0x9d49,
        0x7e97,
        0x6eb6,
        0x5ed5,
        0x4ef4,
        0x3e13,
        0x2e32,
        0x1e51,
        0xe70,
        0xff9f,
        0xefbe,
        0xdfdd,
        0xcffc,
        0xbf1b,
        0xaf3a,
        0x9f59,
        0x8f78,
        0x9188,
        0x81a9,
        0xb1ca,
        0xa1eb,
        0xd10c,
        0xc12d,
        0xf14e,
        0xe16f,
        0x1080,
        0xa1,
        0x30c2,
        0x20e3,
        0x5004,
        0x4025,
        0x7046,
        0x6067,
        0x83b9,
        0x9398,
        0xa3fb,
        0xb3da,
        0xc33d,
        0xd31c,
        0xe37f,
        0xf35e,
        0x2b1,
        0x1290,
        0x22f3,
        0x32d2,
        0x4235,
        0x5214,
        0x6277,
        0x7256,
        0xb5ea,
        0xa5cb,
        0x95a8,
        0x8589,
        0xf56e,
        0xe54f,
        0xd52c,
        0xc50d,
        0x34e2,
        0x24c3,
        0x14a0,
        0x481,
        0x7466,
        0x6447,
        0x5424,
        0x4405,
        0xa7db,
        0xb7fa,
        0x8799,
        0x97b8,
        0xe75f,
        0xf77e,
        0xc71d,
        0xd73c,
        0x26d3,
        0x36f2,
        0x691,
        0x16b0,
        0x6657,
        0x7676,
        0x4615,
        0x5634,
        0xd94c,
        0xc96d,
        0xf90e,
        0xe92f,
        0x99c8,
        0x89e9,
        0xb98a,
        0xa9ab,
        0x5844,
        0x4865,
        0x7806,
        0x6827,
        0x18c0,
        0x8e1,
        0x3882,
        0x28a3,
        0xcb7d,
        0xdb5c,
        0xeb3f,
        0xfb1e,
        0x8bf9,
        0x9bd8,
        0xabbb,
        0xbb9a,
        0x4a75,
        0x5a54,
        0x6a37,
        0x7a16,
        0xaf1,
        0x1ad0,
        0x2ab3,
        0x3a92,
        0xfd2e,
        0xed0f,
        0xdd6c,
        0xcd4d,
        0xbdaa,
        0xad8b,
        0x9de8,
        0x8dc9,
        0x7c26,
        0x6c07,
        0x5c64,
        0x4c45,
        0x3ca2,
        0x2c83,
        0x1ce0,
        0xcc1,
        0xef1f,
        0xff3e,
        0xcf5d,
        0xdf7c,
        0xaf9b,
        0xbfba,
        0x8fd9,
        0x9ff8,
        0x6e17,
        0x7e36,
        0x4e55,
        0x5e74,
        0x2e93,
        0x3eb2,
        0xed1,
        0x1ef0
    );

    function genCRC(&$ptr)
    {
        $crc = 0x0000;
        for ($i = 0; $i < strlen($ptr); $i ++)
            $crc = $this->crc_table[(($crc >> 8) ^ ord($ptr[$i]))] ^ (($crc << 8) & 0x00FFFF);
        $ret = sprintf('%02x%02x', floor($crc / 256), $crc % 256);
        return strtoupper($ret);
    }
}
